Thread:AzureKnight2008/@comment-30866120-20171027080728/@comment-5053743-20171027102218

Well...,

Their species aren't specified in the entire Anime. But since they all belong to the Realm of the Dead a.k.a the UnderWorld of which Engai is the King, you may call them Ghosts or Monsters or Beasts or whatever you like it. ;)